Police in Pureto Rico have interviewed five “persons of interest” as part of their investigation into the stabbing death of a Beavercreek man, who was vacationing with his family during the Christmas holiday.

So far, police said neither the interviews nor the tips from local residents have resulted in leads about the person who killed Brett Walquist, who tried to fight his killer after the intruder broke into the family’s vacation apartment early Monday in the resort community of Rincón.

On Thursday, the Criminal Investigation Corps Aguadilla released a photograph of a baseball cap, with a wooden brim bearing the NFL logo of the Philadelphia Eagles, that was left by the killer following his altercation with Walquist in the apartment. The picture was provided to the Dayton Daily News by the website, PrimeraHora.com.

The Walquist family, reached by telephone Thursday in Grand Rapids, Mich., declined to comment. A family member said they are finalizing funeral arraignments, which should be released later today.

Police Col. Leovigild Vázquez told the website he was authorized by Prosecutor Héctor López to release a picture of the cap in hopes people with information might come forward.

“We tried to find out where they sell this type of hat,” said Police Col. Vasquez Bonilla, who said forensic investigators have worked to extract blood patterns from the hat to identify a suspect.

PrimeraHora.com reported police have searched for potential suspects by reviewing pictures of area people with past burglary convictions who might not be linked to the crime but could help “identify the murderer.”

Police were unsuccessful searching the Caribbean Sea coastline on Tuesday and Wednesday for possible evidence, including the murder weapon, a knife that was taken from the apartment’s kitchen. They are looking for fingerprints the killer might have left on a broken window he climbed through and possibly left on a cell phone that belongs to one of Walquist’s two children.

Walquist, 41, was staying in a first-floor apartment in the Arena y Mar complex with his wife, Gerry, and their two children. The family, who arrived in Puerto Rico on Dec. 17, was scheduled to leave Monday afternoon. The family was on a vacation with Walquist’s father, his sister and her family.

Police said Walquist heard noises inside the apartment and went to investigate at about 1:45 a.m. Monday. When he encountered the intruder, they said a fight ensued, and Walquist was stabbed multiple times by a knife the assailant grabbed from the kitchen.

Police said Walquist’s wife rushed to the kitchen to aid her husband only to find him mortally wounded on the ground. They said she grabbed the attacker, and they both fell to the ground. The killer did not attack Gerry Walquist and escaped through a glass window off the apartment’s terrace. Police said the Walquist’s children were not injured in the attack.